In this paper, the ground heat storage effect on the performance of a SCPP implemented in the South of Tunisia, is investigated. First, a 3D CFD ANSYS-Fluent model is used to study the SCPP performance in the region of Tozeur, which represents the best location in the country, in terms of energy production for a SCPP. Such an installation with a geometry similar to the Manzanares plant, can produce averagely around 150 MWh/year of electrical energy. Subsequently, the study of the effect of the thermal storage on the SCPP performance is presented using an in-house code. In this model, a two-dimensional cylindrical domain is used for the transient conduction in the ground and 1D buoyancy driven flow for the air flow. Such a modeling approach is much more efficient that the full conjugate heat transfer CFD solution obtained through ANSYS-Fluent CFD software and enables the simulation of long term transient behavior. Moreover and for more realistic results, the model uses real weather data for wind speed, ambient temperature and solar radiation. With this model, the performance of three types of ground storage media are investigated. Results show that the ratio between the released and stored energies depends mainly on the season and the energy production is increased by about 35% compared to a system without storage. The results demonstrate the importance of including long-term thermal storage when modelling SCPP.